It is well known that phyllosilicates, such as smectite clays, e.g., sodium montmorillonite and calcium montmorillonite, can be treated with organic molecules, such as organic ammonium ions, to intercalate the organic molecules between adjacent, planar silicate layers, for bonding the organic molecules with a polymer, for intercalation of the polymer between the layers, thereby substantially increasing the interlayer (interlaminar) spacing between the adjacent silicate layers. The thus-treated, intercalated phyllosilicates, having interlayer spacings increased by at least 3 .ANG., preferable at least 5 .ANG., e.g., to an interlayer (interlaminar) spacing of at least about 10-25 .ANG.and up to about 100 Angstroms, then can be exfoliated, e.g., the silicate layers are separated, e.g., mechanically, by high shear mixing. The individual silicate layers, when admixed with a matrix polymer, before, after or during the polymerization of the matrix polymer have been found to substantially improve one or more properties of the polymer, such as mechanical strength and/or high temperature characteristics.
Exemplary prior art composites, also called "nanocomposites", are disclosed in published PCT disclosure of Allied Signal, Inc. WO 93/04118 and U.S. Pat. No. 5,385,776, disclosing the admixture of individual platelet particles derived from intercalated layered silicate materials, with a polymer to form a polymer matrix having one or more properties of the matrix polymer improved by the addition of the exfoliated intercalate. As disclosed in WO 93/04118, the intercalate is formed (the interlayer spacing between adjacent silicate platelets is increased) by adsorption of a silane coupling agent or an onium cation, such as a quaternary ammonium compound, having a reactive group which is compatible with the matrix polymer. Such quaternary ammonium cations are well known to convert a highly hydrophilic clay, such as sodium or calcium montmorillonite, into an organophilic clay capable of sorbing organic molecules.
In accordance with one embodiment of the present invention, intercalates are prepared by contacting a phyllosilicate with a monomeric alkoxylated amine or alkoxylated amide, preferably ethoxylated or propoxylated amine or ethoxylated or propoxylated amide, onium ion spacing/coupling agent compound (hereinafter referred to as an ethoxylated onium ion compound or ethoxylated onium ions). To achieve the full advantage of the present invention, the onium ion should include at least one long chain radical (C.sub.6 +) that may be aliphatic, straight or branched chain, or aralkyl. Exemplary of such suitable C.sub.6 + alkoxylated amine or alkoxylated amide, preferably ethoxylated amine or ethoxylated amide, onium ion molecules (hereinafter referred to as an ethoxylated onium ion compound or ethoxylated onium ions) include primary, secondary, tertiary an quaternary ammonium ions.
In accordance with an important feature of the present invention, best results are achieved by mixing the layered material with the alkoxylated onium ions, e.g., C.sub.6 + onium ion spacing/coupling agent, in a concentration of at least about 0.1% by weight, preferably at least about 0.5% by weight alkoxylated onium ion compound, more preferably at least about 1% by weight to about 10% alkoxylated onium ion compound, and most preferably about 2% to about 10% by weight, based on the weight of alkoxylated onium ion compound and carrier (e.g., water, with or without an organic solvent for the onium ion compound) to achieve better sorption of the alkoxylated onium ion spacing/coupling agent compound between the platelets of the layered material. Regardless of the concentration of alkoxylated onium ion compound in the intercalating composition, the weight ratio of EVOH intercalant:layered material should be at least 1:20, preferably at least 1:10, more preferably at least 1:5, and most preferably at least about 1:4 to achieve sufficient EVOH (or its monomeric reactants) intercalation between adjacent inner surfaces of adjacent platelets of the layered material. The ethoxylated onium ion spacing/coupling agent compound sorbed between and bonded to (or complexed with) the silicate platelets via ion-exchange causes surprisingly easy intercalation of the EVOH polymer, or its monomeric reactants for EVOH polymerization in-situ.
In accordance with an important feature of the present invention, it has been found that an alkoxylated onium ion-intercalated phyllosilicate, such as a smectite clay, can be intercalated easily with EVOH to form an ethoxylated onium ion/EVOH co-intercalate that has excellent intercalate dispersibility in a matrix polymer, particularly an EVOH matrix polymer, and has unexpectedly low gas (particularly O.sub.2) permeability in an EVOH matrix polymer. The intercalate also can be added to any other matrix polymer to enhance a number of properties of the matrix polymer, including tensile strength, heat distortion temperature, gas-impermeability, elongation, and the like.
The alkoxylated onium ion intercalating process of the present invention provides an intercalate that can be added, particularly by direct compounding (mixing the intercalate directly into a matrix polymer melt) of the intercalate into any matrix polymer, e.g., all market available resin systems, including nylons, such as nylon-6 and nylon 66, and particularly EVOH having any desired ethylene content and degree of saponification. In accordance with one important aspect of the present invention, a concentrate composition can be prepared containing the nanomer, comprising the onium ion-intercalated phyllosilicate (0% EVOH), or the concentrated nanocomposite consisting of the onium ion-intercalated phyllosilicate that has been co-intercalated with EVOH, containing 60-90% by weight EVOH (10-40% by weight nanomer, or onium ion-intercalated phyllosilicate, preferably 15-20% by weight nanomer). The nanomer then can be mixed with EVOH matrix polymer, or the nanocomposite mixed with additional EVOH matrix polymer to provide a composition containing a desired percentage of nanomer, generally about 2-7%, preferably 4-6% by weight nanomer for barrier films having unexpected oxygen impermeability.